Milling cutter



E. F. ABER MILLING CUTTER Filed May 30, 1942 v y M? m March 28, 1944.

Patented Mar. 28, 1944 UNITED STATES PATENT OFFICE MILLING CUTTER Earnest F. Aber, Racine, Wis.

Application May 30, 1942, Serial No. 445,172

6 Claims.

This invention relates to improvements in milling cutters.

Heretofore circular milling cutters for certain types of work have been formed with teeth having straight cutting edges extending at alternate rightand left-hand angles transversely of the periphery of the cutter. These cutters are expensive to make because the teeth must be cut therein by feeding a cutting tool transversely of the blank from one side to the other, and even when six blanks are cut at one setting, as is common practice, the time element is substantial. For example, if six blanks each one inch thick are to have teeth cut therein, and are placed side by side, then for each tooth the cutting tool must be fed six inches plus approximately one inch for entrance and one inch for withdrawal movement, or a total of approximately eight inches for each tooth. If the cutters being made are to have twenty-four teeth, then the total feed movement to produce six cutters is twenty-four times eight, or one hundred ninety-two inches.

It is an object of the present invention to provide a milling cutter of the class described wherein the cutting edges of the teeth are arcs instead of straight and wherein said arcs alternate in general angular direction just as the usual straight cutting edges heretofore referred to angle first toward the left and then toward the right. By utilizing the arcuate shape for the cutting edges of the teeth a shear out can be obtained when the finished cutter is used. In

addition an arcuate cutting edge is longer for the same thickness of blank and the corners of the teeth are not subjected to the same breaking strains to which the corners of straight edged teeth are subjected.

In addition to the structural advantages it is found that by utilizing the arcuate teeth of the present invention cutters can be manufactured with a saving of approximately 96% of time, as will hereinafter be pointed out in detail, and it is therefore anobject of the invention to provide a new method of manufacturing cutters involving the use of the arcuate cut to expeditiously produce teeth of the type which alternate in general direction of angularity transversely of the periphery of the blank.

A more specific object of the invention is to provide a method of manufacturing milling cutters of the class described comprising feeding a rotating hollow mill type of cutter into the periphery of the blank with the cutter so supported that its center of rotation is adjacent one side of the blank, and cutting alternate teeth by supporting the rotating cutter with its center of rotation adjacent the opposite side of the blank.

A further specific object of the invention is to provide an improved method of manufacturing cutters of the class described by means of which two cutters may be formed simultaneously. This method comprises placing the sides of two blanks together, feeding a rotating hollow mill type of cutter into the blank with the hollow mill so supported that its center of rotation lies in the plane of the juxtaposed sides of the blank, indexing the blanks and cutting every other tooth, and then shifting the blanks to place the other two sides in contact and repeating the operation to cut the alternate teeth. 7

With the above and other objects in view, the invention consists of the improved milling cutter and methods of manufacturing the same, and all its parts and combinations as set forth in the claims, and all equivalents thereof.

In the accompanying drawing illustrating one complete embodiment of the preferred form of the invention,

Fig. 1 illustrates a side view of a blank showing the last tooth being cut therein, the cutting tool being shown in vertical section and the supporting shaft for the blank being'shown in crosssection;

Fig. 2 is a peripheral view showing two cutters placed side by side to illustrate the method of cutting teeth therein;

Fig. 3 is a similar view with the opposite sides of the blanks in contact to show how alternate teeth are cut; and r Fig. 4 is a fragmentary perspective view of a finished milling cutter.

Referring more particularly to the drawing, the improved cutter is formed of any suitable metal or alloy and comprises a circular blank 8 having a center opening 9 and having peripheral cutting teeth which have cutting edges H), which have a general angle extending to the left (referring to Fig. 4) and alternate teeth having cutting edges l I which have a general angular direction toward the right (referring to Fig. 4). The cutting edges l9 and II instead of being straight are in the form of arcs, as illustrated.

In addition, the cutting edges I ll meet with side cutting edges E2 on one side of the blank and the cutting edges ll meet with similar side cutting edges on the opposite side of the blank. Re-

ferring to Fig. 4, the material on the side tapers inwardly as 'at [3 so that the thickness is reduced in front of the next side cutting edge l2. Thus there are side channels through which a cutting compound can flow during use. In addition the side cutting edges which extend in a generally radial direction provide for cutting at right angles to the axis of the cutter 8, when the latter is used, in addition to the cuts produced by the cutting edges Ill and l Due to the fact that one tooth projects toward one side and the next tooth toward the opposite side, this type of cutter is generally called a staggered tooth side milling cutter. Also because of the angular directions of extent of the cutting edges ii! and II, this type of cutter is generally referred to as a spiral mill. However, on all spiral mills heretofore manufactured the cutting edges I and I l have been straight lines and not arcs.

The peripheral cutting edges H), which constitute every other cutting edge, are the arc of a circle whose center It is positioned toward one side of the blank, and the alternate cutting edges H are the arcs of circles whose centers is are positioned toward the opposite side of the blank. In the preferred form of the invention illustrated, the centers M actually lie in the plane of one side of the blank and the centers I5 lie in the plan of the opposite side of the blank.

In addition, in the preferred embodiment of the invention the cutting edges It are equal to one-half of an arc (comprising two of the arcs H) as in Fig. 2), whose chord I6 is bisected by the plane of one side of the blank, it being obvious that the chord I5 is bisected by the line H.

Referring to Fig. 3, the alternate cutting edges H are arcs which are one-half of an arc whose chord I8 is bisected by the line 19 or by one side of the blank.

In manufacturing the improved cutters a circular cutting tool 20 is utilized having teeth 2! formed with cutting edges 22. This cutting tool is mounted on a rotating shaft 23, and the shaft is supported as shown in Fig. 1 with respect to the blank 8. To cut the cutting edges I! the supporting shaft 23 for the cutting tool 2 is supported so that the center of rotation of the cutt ng tool '20 is toward one side of the blank, and when properly set every other tooth, or the teeth I! are all cut in the blank by suitably indexing the blank after each tooth is cut. After the teeth II have been out, then either the cutting tool or the blank is shifted so that the center of rotation of the cutting tool is adjacent the opposite side of the blank. The alternate teeth or the teeth having the cutting edges I 9 are then all cut, the blank being suitably indexed after each tooth is completed.

To obtain more speedy production it is an important feature of the present invention to utilize the method of Figs. 2 and 3 wherein the teeth are cut in two blanks simultaneously. When this method is used two of the blanks 8 and 8' are placed with their sides together, as shown in Fig. 2, and the supporting shaft 23 of the cutter is so adjusted that the center of rotation of the tool 20 lies in the plane of the juxtaposed sides of the blanks 8 and 8, as indicated by the centers I 4 of Fig. 2. When this setting is obtained the teeth having the cutting edges III are cut in both blanks simultaneously, and it will be seen from Fig. 2 that the curve of the cutting edge It on the blank 8 continues into the curve of the cutting edge IO of the blank 8. Thus equal arcs ill are cut in both of the blanks simultaneously. After one tooth is cut to a desired depth the tool is withdrawn and the blanks are indexed simultaneously skipping one space to cut the next set of arcs It. After all of the arcs l0 have been cut, then the blanks 8 and 8' are reversed in position, as shown in Fig. 3, so that their opposite sides are in contact and the sets of teeth having cutting edges I! are cut into the blanks, using the centers l5 for the center of rotation of the cutting tool 29. These centers I5 of Fig. 3 are on opposite sides of both blanks from the centers M of Fig. 2, and the centers it: are in the plane of the juxtaposed sides of the blanks of Fig. 3.

The side or radial cutting edges l2 may be formed in the usual manner.

It is apparent that with the above method of cutting teeth in the two blanks simultaneously, clue to the fact that the teeth are cut on arcs, results in a great saving of time over the method of forming the old type of spiral mill having straight peripheral cutting edges. With the improved method, assuming that the teeth are inch deep, the rotary cutting tool 2i must be fed inch to cut one tooth in two blanks. To cut twenty-four teeth in two blanks the total feed movement is six inches. If it is desired to produce six milling cutters the operation must be repeated three times, with a total feed movement of the tool 28 of eighteen inches. This eighteeninch feed movement compares with the one hundred ninety-two inches of feed movement required to make six spiral mill cutters of the old type having straight peripheral cutting edges.

When using the finished cutter it is of course rotated in a clockwise direction, referring to Fig. l, which causes the curved cuttinr edges Iii and l i to produce a shear out which is more efiicient than the shear type of cut produced by an angled straight edge. In addition there is very little strain on the corners of the curved teeth during use, and these teeth therefore resist breakage to a marked degree. Furthermore, the curved cutting edge is a longer edge for the same thickness blank than a straight cutting edge. The present invention therefore not only produces a more desirable type of milling cutter than heretofore manufactured but also produces the more desirable type with the expenditure of substantially less time and therefore at less cost.

The invention comprehends other forms of the structure and modifications of the method and is therefore not intended to be limited to the precise structure and methods above described, except as required by the appended claims.

WVhat I claim is:

1. A circular milling cutter having cutting teeth on its periphery, the cutting edges of said teeth being arcs, the arc of every other tooth throughout the length of said tooth being the arc of a circle whose center is positioned toward one side of the cutter, and the arc of each alternating tooth throughout the length of said tooth being the arc of a circle whose center is positioned toward the opposite side of the cutter.

2. A circular milling cutter having cutting teeth on its periphery, the cutting edges of said teeth being arcs, the arc of every other tooth being one-half of an arc whose chord is bisected by the plane of one side of the cutter, and the arc of each of the alternating teeth being one-half of an arc whose chord is bisected by the opposite side of the cutter.

3. A circular milling cutter having a cutting tooth on its periphery, said tooth having a cutting edge which is the arc of a circle whose center is positioned nearer to one side of the cutter than to the other, so as to provide a relatively fiat are at the leading end of the cutting edge.

4. A circular milling cutter having a cutting tooth on its periphery, said tooth having a cutting edge which is approximately one-half of an arc whose chord is bisected by the plane of one side of the cutter, to thereby provide a relatively fiat arc at the leading end of the cutting edge.

5. A circular milling cutter having cutting edges projecting laterally from each side, said cutter also having cutting teeth on its periphery, the cutting edges of said peripheral teeth being arcs, the arc of every other tooth being the arc of a circle whose center is positioned nearer to one side of the cutter than the other, and the arc of each alternating tooth being the arc of a circle whose center is positioned nearer to the opposite side of the cutter, so as to provide relatively flat arcs at the leading ends of the cutting edges, said leading ends meeting the side cutting edges.

6. A circular milling cutter having laterally projecting cutting edges on each side, said cutter also having cutting teeth on its periphery, the cutting edges of said peripheral teeth being arcs, the arc of every other tooth being approximately one-half of an arc whose chord is bisected by the plane of one side of the cutter, and the arc of each of the alternating teeth being approximately one-half of an arc whose chord is bisected by the opposite side of the cutter, said arcs providing relatively flat arc portions at the leading ends of the peripheral cutting edges, and said are portions meeting the side cutting edges.

EARNEST F. ABER. 

